1. Field of the Invention
The present invention is directed to a heating and spraying system for highly viscous liquid and more particularly to the heating and spraying of cold process roof material to an optimum temperature for dispensing irregardless of the ambient temperature.
2. Brief Description of the Prior Art
Tar pitch and asphalt have been heated or liquified for application to roofs for a long period of time in the roofing industry. A kettle or vat holding the asphalt has been heated by a burner fired heater tube system positioned on the bottom of the vat. This design permits the bituminous material to cover and surround the heating tube system. Generally, the tar or asphalt would be placed in a solid state on top of the heating tubes and the passing of hot gases through the tubes would liquify the material for ultimate spreading on a roof.
The Chausse U.S. Pat. No. 2,506,412 represents an improvement on the basic kettle design for the purpose of both transporting and dispensing tar and asphaltic oils under low ambient temperature conditions. In this reagrd, a regard, of tanks are provided adjacent a central heat transfer vat. Compressed air tanks are also provided for ejecting the material from the storage tanks. A closed hot oil transfer system is utilized wherein hot transfer oil is heated in a coil and then piped to the central heat transfer tank for heating the asphalt material.
The Miller U.S. Pat. No. 2,690,172 and U.S. Pat. No. 2,729,209 both disclose apparatus for transporting and heating asphalt. The asphalt tanks are designed to permit a heating liquid to pass through pipes mounted within storage tanks.
The Loebel U.S. Pat. Nos. 3,111,935 and 3,196,841 disclose heaters for asphalt wherein a hot gas helical flue pipe is utilized to heat the asphalt while an outer bath of heat transfer oil is circulated to control the heat exchange.
Finally, the Hynes et al U.S. Pat. No. 3,281,573 discloses a heating system for asphalt equipment, wherein electric coils are utilized to selectively store, or withdraw, heat from the asphalt.
Recently, cold processing roofing material has been developed to replace the asphalt and tar commonly utilized as roofing material. An example of such material is the GAF Corporation MINERAL SHIELD MASTIC, this material purportedly provides a great advantage over the tar pitch and asphaltic oils, utilized previously, in that less man power is required to apply the material and less equipment is needed, since it eliminates hot carriers, gravel handling equipment and kettles. The cold processing material has been described as a filled asphalt or coal tar with solvents having material such as asbestos added to it.
An additional advantage of cold processing material is that pollution is reduced, since the fumes and smoke that are associated with an asphaltic oil or bituminous material is greatly reduced. In addition, it is asserted that the potential for blistering problems when applied to the roof and the criticality of the application of the material is greatly lessened. This cold processing roofing material, however, is relatively temperature sensitive and a cold ambient temperature will greatly increase the viscosity of the material to the point where its application will be prohibited in the Winter months in cold climates. Frequently, it is recommended that the cold processing material be cut with a solvent to increase its flowability and lessen its viscosity. This, however, raises further problems, such as the criticality of the mixing of proportions of the appropriate solvent and the necessity to permit the solvent to evaporate before sheets of the roofing material can be applied or else gas pockets will form under the sheets. Cold processing roofing material that has been cut with too much solvent will flow too easily and produce a resulting thin applied layer of material.
In addition, the spraying equipment which is recommended to be utilized with cold processing material, such as the Mineral Shield Mastic, must be either an internal or external mix system for combining the material with air to atomize the material. As noted by the manufacturer of the above material, airless equipment is not recommended for the distribution of Mineral Shield Mastic, due to its long fiber content and its consistency. It should be realized that when roofing contractors are spraying cold process material, they are frequently dealing with the pumping of the material over a relatively large distance e.g., 200 to 500 feet with a relatively large vertical elevation.
In the field of airless spraying apparatus the following patents are cited of general interest: Glaros -- U.S. Pat. No. 3,469,788, Kocher -- U.S. Pat. No. 2,631,891 and U.S. Pat. No. 3,197,144, Wagner -- U.S. Pat. No. 3,515,355 and Christian -- U.S. Pat. No. 2,923,480. The use of airless equipment for material having the viscosity of cold processing material would generally require an extremely high pressure system to atomize the material at the spray nozzle.
As a result of the low viscosity of the heated cold process material, any air or hydraulically operated pump may be used in the spraying operation. The present invention provides a system of changing the viscosity of highly viscous liquids or semi solids such as coal tars, asphalts, bituminous paints, urethanes, polymeric material, etc. and more particularly cold processing roofing material.
With respect to the cold processing roofing material that was formerly applied by changing the viscosity of the material through the dangerous process of thinning with solvents or the possible over heating or scorching of the material with a direct flame to the barrel or heating in direct flame asphalt kettles, the present invention provides a significant improvement in the conventional application of the material. This is accomplished by a controlled heating of the cold process roofing material in a highly efficient manner to facilitate spraying.